Method of making a finished product

ABSTRACT

A method of making a finished product includes the steps of providing a feedstock comprising a polymer component comprising 5 to 100 parts by weight of a polymer selected from the group consisting of polyethylene in particulate form, polyvinyl chloride in particulate form, and a mixture of polyethylene and polyvinyl chloride both in particulate form; 0 to 95 parts by weight of polystyrene in particulate form; an extender, and optionally reinforcing fibres or particles; mixing the feedstock with a thermosetting resin selected from an unsaturated polyester resin in liquid form and a catalyst for the polyester resin and an epoxy resin in liquid form and a catalyst for the epoxy resin; and subjecting the product to suitable conditions of temperature and pressure to cause the polyethylene and/or the polyvinyl chloride and the polystyrene, if present, to melt and the thermosetting resin to set to form the finished product, e.g a shutter board.

BACKGROUND OF THE INVENTION

This invention relates to a method of making a finished product and tothe finished product so made.

It is well known to use wood and wood products to manufacture manydifferent types of finished products. For example, wood fibres may beused to mould door skins, solid wood may be used to make mouldings,window, frames, wall studding, decking, roof support rafters andbrandering, plywood may be used for bulk handling bins, and the like. Inaddition, certain plastic materials may also be used to make structuralitems. For example, polyvinyl chloride may be used for the constructionof sidings and window frames.

However, with the modem requirement for recyclability and the tendencyfor wood products to absorb water which results in thickness swell aswell as microbial growth and a reduction in strength, there is a needfor new products to replace such wood products.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a methodof making a finished product including the steps of:

-   -   (a) providing a feedstock comprising:    -   (1) 10 to 40 parts by weight of a polymer component comprising:        -   (i) 5 to 100 parts by weight of a polymer selected from the            group consisting of polyethylene in particulate form,            polyvinyl chloride in particulate form, and a mixture of            polyethylene and polyvinyl chloride both in particulate            form; and        -   (ii) 0 to 95 parts by weight of polystyrene in particulate            form;    -   (2) 10 to 70 parts by weight of a particulate extender; and    -   (3) 0 to 40 parts by weight of reinforcing fibres or particles;    -   (b) mixing the feedstock with 10 to 35 parts by weight of a        thermosetting resin selected from the group consisting of:        -   (i) an unsaturated polyester resin in liquid form and a            catalyst for the polyester resin; and        -   (ii) an epoxy resin in liquid form and a catalyst for the            epoxy resin; and    -   (c) subjecting the product of step (b) to suitable conditions of        temperature and pressure to cause the polyethylene and/or the        polyvinyl chloride and the polystyrene, if present, to melt and        the thermosetting resin to set to form the finished product.

According to a second aspect of the invention there is provided afinished product comprising a feedstock comprising:

-   -   (1) 10 to 40 parts by weight of a polymer comprising:        -   (i) 5 to 100 parts by weight of a polymer selected from the            group consisting of polyethylene in particulate form,            polyvinyl chloride in particulate form, and a mixture of            polyethylene and polyvinyl chloride both in particulate            form; and        -   (ii) 0 to 95 parts by weight of polystyrene in particulate            form    -   (2) 10 to 70 parts by weight of a particulate extender; and    -   (3) 0 to 40 parts by weight of reinforcing fibres or particles;        bound with 10 to 35 parts by weight of a thermosetting resin        selected from the group consisting of:        -   (iii) an unsaturated polyester resin in liquid form and a            catalyst for the polyester resin; and        -   (iv) an epoxy resin in liquid form and a catalyst for the            epoxy resin.

Preferably, the feedstock comprises:

-   -   (1) 15 to 35 parts by weight of the polymer component;    -   (2) 15 to 50 parts by weight of the extender;    -   (3) 0 to 25, preferably 10 to 25 parts by weight of the        reinforcing fibres or particles;    -   mixed with 15 to 25 parts by weight of the thermosetting resin.

It is to be noted that the finished product does not contain anyhydraulic binder. In other words, the method of making the finishedproduct is carried out without the use of a hydraulic binder and thefinal finished product does not include a hydraulic binder.

It is also to be noted that the method of the invention is carried outwithout the use of water at any stage.

The polymer component of feedstock may comprise polyethylene on its own,or polyvinyl chloride on its own, or a mixture of polyethylene andpolyvinyl chloride without any other polymer, or any one ofpolyethylene, polyvinyl chloride or a mixture of polyethylene andpolyvinyl chloride, together with an amount of polystyrene, all being inparticulate form.

The polymer component of the feedstock preferably comprises:

-   -   (i) 40 to 100 parts by weight of a polymer selected from the        group consisting of polyethylene in particulate form, polyvinyl        chloride in particulate form, and a mixture of polyethylene and        polyvinyl chloride both in particulate form; and

(ii) 0 to 60 parts by weight of polystyrene in particulate form.

The polymer component of the feedstock more preferably comprises:

-   -   (i) at least 50 parts to 100 parts by weight of a polymer        selected from the group consisting of polyethylene in        particulate form, polyvinyl chloride in particulate form, and a        mixture of polyethylene and polyvinyl chloride both in        particulate form; and    -   (ii) 0 up to 50 parts by weight of polystyrene in particulate        form.

The polyethylene and/or polyvinyl chloride provides the finished productwith impact and flexural strength while the polystyrene provides thefinished product with rigidity and hardness.

Depending upon the end use to which the finished product is to be put,the relative quantities of polyethylene, polyvinyl chloride andpolystyrene may be varied to give a finished product with the desiredproperties.

The polyethylene may be chosen from linear low density polyethylenethrough to high density polyethylene.

The polyvinyl chloride may be any suitable polyvinyl chloride and ispreferably a polyvinyl chloride that has been compounded with astabiliser to prevent decomposition at the temperatures used in themethod of the invention, and with a lubricant to propagate flow prior toand during the polymerisation of the thermosetting resin and to blendwith the other components of the composition.

The polystyrene is preferably milled polystyrene foam or polystyrenepackaging.

The polyethylene, polyvinyl chloride and polystyrene must be inparticulate form. By “particulate form” is meant round or flatparticles, granules, and short fibres, all having a maximum dimension of3 mm. The polyethylene, polyvinyl chloride and polystyrene arepreferably used in powder form and preferably have a particle size of1.0 mm diameter or less, more preferably 0.5 mm diameter or less.

The extender may be selected from the group consisting of a lightweightinorganic volume extender, a lightweight organic volume extender, andmixtures of two or more thereof.

The extender may also be milled mineral particles.

By a volume extender there is meant a particulate product with a lowbulk density which when added to the composition of the inventionincreases its compression ratio, i.e the thickness of the product beforepressing to the thickness of the product after pressing. The greater thecompression ratio the greater is the control over product density,because the more the particles are pressed together, the better is thecohesion of the final product.

Volume extenders serve other useful functions including minimisinglateral flow of the composition of the invention during compressionmoulding, as a function of its thermoplasticity.

In the composition of the invention, the use of volume extenders ofdifferent bulk densities and particle sizes allows for maximumflexibility in formulating a product for a particular application.

The lightweight volume extender may be selected from hollow glassballoons, milled expanded perlite particles, undensified silica fume,exfoliated vermiculite particles, cork particles, leather particles, anda mixture of two or more thereof.

The extender, as indicated above, may also be milled mineral particlesselected from the group consisting of calcium carbonate particles,silica particles, expanded clay particles, and the like.

The reinforcing fibres or particles may be selected from inorganic ororganic fibres or particles.

As indicated above, the thermosetting resin may be selected from thegroup consisting of an unsaturated polyester resin and an epoxy resin.

The preferred thermosetting resin is an unsaturated polyester resin inliquid form with a catalyst for the polyester resin, for the reasons ofcontrolled temperature of polymerisation initiation and minimal volatileproducts on polymerisation.

The extender is most preferably an inorganic extender, so as to avoidproblems associated with the use of organic extenders.

The method of the invention may include a step between step (b) and step(c), of placing the product of step (b) on a first length of a sheetmaterial or between first and second lengths of a sheet material so thatin step (c) the first length and the second length, if present, areincorporated into the finished product.

Alternatively, the method of the invention may include a step after step(c) of:

(a) placing the finished product on a first length of a sheet materialor between first and second lengths of a sheet material with a layer ofa thermosetting resin between the finished product and the first lengthand the second length, if present, and subjecting the resulting productto suitable conditions of temperature and pressure to laminate the firstlength to the finished product and to laminate the second length, ifpresent, to the finished product, to form a composite product.

The sheet material may be for example a resin impregnated paper or anon-woven or woven fabric or the like, or a thermoplastic sheetmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view of a hydraulic press being used for themanufacture of a door skin of the invention;

FIG. 1B is a side view of two door skins manufactured in the hydraulicpress of FIG. 1A;

FIG. 2A is a schematic view of a hydraulic press being used for themanufacture of a moulding for window frames of the invention;

FIG. 2B is a sectional side view of window frame mouldings manufacturedin the hydraulic press of FIG. 2A;

FIG. 3 is a sectional side view of a wall stud of the invention;

FIG. 4 is a sectional side view of decking of the invention;

FIG. 5A is a sectional side view of a sheet which may be cut to formsiding strips of the invention; and

FIG. 5B is a sectional side view of an assembly of the siding strips ofFIG. 5A.

DESCRIPTION OF EMBODIMENTS

The crux of the invention is a method of making a finished product froma feedstock comprising a polymer component comprising polyethylene inparticulate form and/or polyvinyl chloride in particulate form andoptionally polystyrene in particulate form, an extender, and optionallyreinforcing fibres or particles, by mixing the feedstock with athermosetting resin and a catalyst for the resin. Thereafter the productis subjected to suitable conditions of temperature and pressure to causethe polyethylene and/or polyvinyl chloride and the polystyrene, ifpresent, to melt and the thermosetting resin to set to form the finishedproduct.

The first component is a feedstock comprising a polymer componentcomprising polyethylene and/or polyvinyl chloride and optionallypolystyrene in particulate form.

The polyethylene may be for example a linear low density polyethylenefor a finished product with toughness and flexibility or a high densitypolyethylene for a finished product with high rigidity.

The polyethylene may be either virgin polyethylene or, more preferablyin terms of cost, be recycled or post industrial grade polyethylene,reduced to a relatively small particle size. When the polyethylene comesfrom a waste stream, it is acceptable for the waste stream and thus thepolyethylene in the feedstock to contain a quantity of other polymersfrom the waste stream, such as, polyethylene terephthalate from bottles,polypropylene, polycarbonates, and polyesters. These additional wastepolymers act as extenders for the feedstock in the finished product, asthey generally have melting points higher than the temperatures used instep (c) of the method of the invention.

For example, polyethylene teraphthalate chips or fibres with a maximumdimension of 10 mm act advantageously as an extender in a finishedproduct of the invention.

The polyethylene melts and commences to flow in the temperature range offrom 115° C. to 140° C. inclusive.

The polyethylene must be in particulate, preferably powder form.Preferably, the polyethylene particles have a particle size of 1.0 mm indiameter or less, more preferably 0.5 mm in diameter or less, mostpreferably 150 microns in diameter or less.

The polyvinyl chloride may be for example a polyvinyl chloride that hasbeen compounded with a stabiliser to prevent decomposition at thetemperatures used in the method of the invention and with a lubricant topropagate flow prior to and during the polymerisation of thethermosetting resin and to blend with the other components of thecomposition. An example of a suitable polyvinyl chloride is DB178 byPolifin Division of Sasol, South Africa.

The properties of DB178 extrusion grade PVC are:

TYPICAL PROPERTIES UNIT VALUE TEST METHOD Relative Density 1.43 SABSMethod 649 Shore D Hardness 83 ASTM D2240 Vicat Softening Point ° C. 85ASTM D1525 Tensile Strength N/mm² 38 BS2782 - 1970 Elongation % 49BS2782 - 1970 Volume Resistivity @ Ωcm 28 × 10¹⁵ ASTM D257 23° C. FireRating Self extinguishing Ash Content @ 650° C. % 4.30

The polyvinyl chloride melts and commences to flow in the temperaturerange of from 150° C. to 185° C.

The polyvinyl chloride must be in particulate, preferably powder form.Preferably, the polyvinyl chloride particles have a particle size of 1.0mm in diameter or less, more preferably 0.5 mm in diameter or less, mostpreferably 150 microns in diameter or less.

The polystyrene is preferably milled polystyrene foam or polystyrenepackaging from a waste stream.

Polystyrene is a clear glass-like material manufactured by the freeradical polyimerisation of phenylethene using benzoyl peroxide as aninitiator. It has excellent thermal and electrical insulation propertiesand, in the method of the invention after having melted, it sets oncooling to a very hard inflexible, glass-like solid which is extremelyresistant to water, having a water absorption after 24 hours ofimmersion of less than 0.06% by weight.

The polystyrene melts and commences to flow in the temperature range offrom 100° C. to 140° C. inclusive.

The polystyrene must be in particulate, preferably powder form.Preferably, the polystyrene particles have a particle size of 1.0 mm indiameter or less, more preferably 0.5 mm in diameter or less, mostpreferably 150 microns in diameter or less.

The properties of polyethylene, polyvinyl chloride polystyrene and otherpolymers are set out in the table below.

Typical physical and mechanical comparisons between thermoplastics at23° C. are as follows:

Degree Coefficient of Glass of Thermal Transition Density Crystal-Expansion Temp. Material (g/cm³) linity Comparisons (° C.) Poly-0.95–0.97 high 8.3–16.7 −120 ethylene High- density Poly- 0.92–0.93moderate 8.9–11.0 −120 ethylene Low- density Poly- 0.90–0.91 high 6.2−20 propylene Poly- 1.0–1.1 nil 100 stryene Polyvinyl 1.3–1.6 nil2.8–3.3  85 Chloride Un- plasticized (PVC) Poly- 2.1–2.2 moderate 126tetra- to fluoro- high ethylene

Crystal Melting Tensile Elongation Flexural Temp Strength at BreakModulus Material (° C.) (MPa) (%) (GPa) Polyethylene 137 20–30  10–1000 1–15 High-density Polyethylene 110  8–30 100–650 0.25–0.35 Low-densityPolypropylene 176 30–40 100–600 1.2–1.7 Polystyrene — 35–50 1–2 2.6–3.4Polyvinyl Chloride — 40–50  2–80 2.1–3.4 Unplasticized (PVA)Polytetrafluroroethylene 327 20–35 200–400 0.5

The feedstock also includes an extender.

The extender may be a lightweight inorganic volume extender such ashollow glass balloons, generally sourced from ground coal firing, whichare siliceous, with a low bulk density in the range of from 200 g/l to300 g/l and with a particle size in the range of from 50 to 300 microns,an example being Fillite SG; or milled expanded perlite particles suchas Dicalite 411 or 471 by Chemserve Perlite South Africa, which has asimilar bulk density to hollow glass micro balloons; or undensifiedsilica fume with a bulk density in the range of 200 g/l to 300 g/l; orexfoliated vermiculite particles such as RSU by Palaborwa or MCF byImerys, preferably with a particle size of less than 300 micron.

The extender may also be a lightweight organic volume extender such asparticles of cork or leather with bulk densities in the range of from150 to 250 g/l inclusive.

The extender may also be milled mineral particles such as for examplecalcium carbonate, silica or expanded clay particles.

The extender may be a blend of two or more of the above.

The purpose of adding an extender to the feedstock is to control thedensity of the finished product with a minimum reduction in stiffness,and to minimise the coefficient of linear expansion in order to achieveacceptable dimensional stability, to improve stiffness and impactresistance, and to reduce cost.

The extender is preferably an inorganic extender selected from those setout above.

The most preferred extenders are selected from the group consisting ofhollow glass balloons, expanded clay particles, exfoliated vermiculiteparticles and expanded perlite particles.

The feedstock may also comprise reinforcing inorganic particles orfibres such as glass fibre, either milled or up to 16 mm in length, butpreferably of the order of 12 mm in length for best distribution andreinforcing; platelet minerals such as mica, preferably with a particlesize in the range of 8 to 100 mesh, more preferably about 40 mesh, orphlogopite; or rod-like particles such as wollastonite.

The feedstock may also comprise reinforcing organic particles or fibressuch as lignocellulosic fibres, e.g typha reed fibres, kenaf, flax,sisal and wood; or synthetic fibres such as polyester fibres capable ofwithstanding pressing temperatures in excess of 160° C.

The reinforcing fibres may be a blend of two or more of the above.

The next component is a thermosetting resin.

The first thermosetting resin which may be used is an unsaturatedpolyester resin in liquid form and a catalyst for the polyester resin.

An example of a suitable polyester resin is a high reactivity resin forhot pressed dough moulding compound applications (DMC), which resin isan orthophthalic, unsaturated polyester resin designed for use in themanufacture of glass and aggregate filled dough moulding compounds. Itmay be used in conjunction with low profile/low shrink additives forzero or low shrink hot press moulded products. Typical properties ofthis resin are a viscosity at 25° C. of 1470 mPa·s, a volatile contentof 35.5%, and a curing characteristic at 126° C. using one part perhundred of Triganox 29B50 catalyst of a five minute gel time.

Another suitable resin is a chemical and water resistant isophthalic,neo-pentyl glycol unsaturated polyester resin used for high performancelaminates. An example of this resin is NCS 993 by NCS Resins SouthAfrica, which has a viscosity at 25° C. of 540 to 800 mpa·s, an acidvalue of 10 to 16 mgKOH/g, a volatile content of 39 to 43%, which may becured with a latent catalyst such as Triganox 29B50 which is a benzoylperoxide.

Other suitable polyester resins include Crystic 272 and Crystic 196 fromScott Bader, England, catalysed by catalyst powder B; those sold underthe Atlac brand from DSM; Polyite 33410, Polylite 8130, Polylite 8000and Polylite 8382X from National Chemical Products, South Africa,catalysed with di-tert-butyl peroxy 3,3,5-tri-methylcyclohexane indibutyl phthalate such as Triganox 29B240, Lucidol KL50, Triganox 21,Triganox C or Triganox K-70, benzoyl peroxide formulations, t-butylperbenzoate from Interox, e.g Codes TBTB and TBPB, dibenzoyl peroxidefrom Interox Code BP.50-FT, and methyl isobutyl ketone peroxide fromInterox under Code MIKP NA1. These catalysts generally triggerpolymerisation at a temperature in the region of 60° C. upwards, moretypically 80° C. upwards.

The catalyst for the unsaturated polyester resin is preferably used inan amount of from 0.5% to 2.5% to 100% of the unsaturated polyesterresin on a weight basis.

The second thermosetting resin which may be used is an epoxy resin inliquid form and a catalyst for the epoxy resin. A preferred epoxy resinis a low viscosity liquid epoxy resin manufactured from epichlorohydrinand bisphenol F. Typical examples of such resins include thosemanufactured by Shell Chemical Company under the names Epikote 816, 862,232, 235 and 236, and those manufactured by Ciba-Geigy AG under thenames XD.4150, XSA.214, Araldite AZ.15 and Araldite PY.340-2. Othersuitable epoxy resins include epoxy resins with blocked amine functions,such as the reaction product of phthalic anhydride with diethylenetriamine.

Suitable latent catalyst systems for use with epoxy resins include thosecatalyst systems supplied by Anchor Chemicals (UK) Limited such asAncamine 2014S which is a modified polyamine; Anchor/catalyst 1786Bwhich is 50/50 solution of p-toluene sulphonate of2-amine-2-methyl-1-proponal in n-butanol.

These catalysts generally trigger polymerisation at a temperature ofaround 80° C. or upwards.

The unsaturated polyester resin may optionally be mixed with up to 50%by weight of the polyester resin of a styrene monomer for viscositymodification.

In order to propagate the adhesion between the polyethylene, polyvinylchloride and polystyrene, i.e to induce the formation of a physicalco-polymer between them and in order to impose upon the finished productimproved toughness, and shock resistance when polystyrene is used inrelatively large proportions, the product of the invention may include athermoplastic elastomer, also known as a thermoplastic rubber or blockco-polymer.

The thermoplastic elastomer is preferably used in an amount of from 2.5%to 35.0% based on 100% by weight of the polystyrene present.

The thermoplastic elastomer is preferably dissolved in a styrene monomerto produce a saturated solution. This saturated solution is thenpreferably blended with the thermosetting resin and its catalyst beforethis is added to the feedstock.

Examples of suitable thermoplastic elastomers are those having styreneend blocks and an elastomeric mid-block such as for example butadiene,isoprene, ethylene and the like, i.e those that have two differentpolymers in each molecule. Thus for example, suitable thermoplasticelastomers include a styrene/butadiene/styrene polymer, astyrene/isoprene polymer, and an acrylonitrile/butadiene/styrenepolymer. The preferred thermoplastic elastomers are thestyrene/butadiene polymers. Specific examples of suitable thermoplasticelastomers are the Kraton grades by Shell Chemicals. The “D” series areunsaturated and suitable for interior application and are comprised ofstyrene/isoprenelstyrene block copolymers which are linear, andstyrene/butadiene radial copolymers. The “G” series are fullyhydrogenated grades for exterior applications and includestyrene-ethylene/butylene-styrene block co-polymers which are linear andstyrene-ethylene/propylene di-block polymers. The Kraton “G” range ofthermoplastic elastomers possess excellent resistance to oxygen, ozoneand UV light degradation.

In addition, the propagation of adhesion between the thermosettingresin, polyethylene, polyvinyl chloride and polystyrene and anyinorganic extender present may be further induced by the use of a silanecoupling agent or crosslinker. An example is DC 1107 by Dow Corning usedin an amount of about 0.5% on the weight of the thermosetting resin.This is a solvent soluble polymethylhydrogen siloxane. A further exampleis a gamma-methacryloxypropyltrimethoxy silane, Silquest A.174 silane byWitco Corporation which is specific to polyolefin to polyester toinorganic linkage, used in an amount of 0.1% by weight of the totalcomposition.

In an alternative step, after step (c) the finished product may beplaced on a first length of a sheet material or between first and secondlengths of a sheet material, with a layer of a suitable thermosettingresin between the first length and the second length, if present, andthe finished product, whereafter the whole is subjected to suitableconditions of temperature and pressure to laminate the first and secondlengths of the sheet material to the finished product to form acomposite product.

In step (b) of the method of the invention, the feedstock and thethermosetting resin are mixed.

It is to be noted that the finished product of the invention contains nohydraulic binder such as Portland cement.

In step (c) of the method of the invention, the product of step (b) issubjected to suitable conditions of temperature and pressure to causethe polyethylene and/or polyvinyl chloride and polystyrene, if present,to melt and the thermosetting resin to set to form the finished product.

Suitable conditions of temperature and pressure include a temperature offrom 110 to 200° C. inclusive and a pressure of from 10 to 50 kg/cm²inclusive. For example, the product of step (b) may be laid up betweenthe platens of a press, and pressed to form a finished board product.

The exotherm from the thermosetting resin polymerization can elevate thecomposition temperature to above that of the platen temperature. Coolingof the product prior to releasing press platen contact is desirable toallow full strength and stability of the product to develop beforehandling.

Alternatively, the product of step (b) may be placed in a suitable mouldand moulded to form a finished moulded product.

Further alternatively the product of step (b) may be extruded.

In a variation of the method of the invention, between step (b) and (c),the product of step (b) may be placed on a first length of a sheetmaterial or between first and second lengths of a sheet material so thatin step (c) the first length and the second length, if present, areincorporated into the finished product.

For example, the product of step (b) may be placed between first andsecond lengths of a sheet material, each length consisting of single ormulti layers of a resin impregnated paper, preferably saturating Kraftpaper impregnated with a resin selected from:

-   -   1 An unsaturated polyester resin with a catalyst therefor,        optionally extended with a styrene monomer, in a solvent such as        acetone. An example of a suitable unsaturated polyester resin is        a neo-pentyl glycol unsaturated polyester resin, viz. NCS 993 by        NCS Resins South Africa, in acetone, optionally including up to        10% by weight of a styrene monomer and also containing 0.5% to        2.5% by weight of the polyester resin of Triganox 29B50        catalyst.    -   2 A phenol formaldehyde resole resin such as Code J2018L by        Borden Chemical Corporation, with an acid catalyst such as        Phencat 10, (preferably in an amount of about 6% by weight of        the resin) in methanol.    -   3 An MDI which is a diphenylmethane-4,4-diisocyanate, for        example Suprasec 5005 or 2447 by Huntsman Corporation,        optionally including a catalyst, in a suitable solvent such as        acetone, ethyl acetate or dichloromethane

The sheets of paper are impregnated with the resin system, whereafterthe solvent is removed.

In step (c), the impregnated lengths of paper are then incorporated intothe product of step (b) using suitable conditions of temperature andpressure as described above.

The Kraft paper preferably has a weight of about 200 to 400 g/m² and athickness of approximately 350 to 500 microns.

Alternatively, and particularly where the finished product is to beshaped, for example to form a corrugated pallet deck, a non-wovenfibrous sheet, preferably made of a polyester or polyethyleneteraphthalate, which both have melting points in excess of 245° C., maybe used in place of the Kraft paper. These non-woven fibrous sheets mayoptionally be pre-impregnated with the same impregnating compositionsdescribed above for paper.

An example of a suitable non-woven fibrous material is Bidim Geotextileby Kaytech (Code A2 to Code A6) with a weight of 150 to 340 g/m², atensile strength of 11 to 30 kNm, an elongation of 40% to 60% (which isnecessary in pressing a shape to allow the accommodation of theincreased surface area during compression moulding), and a melttemperature of about 250° C.

Other examples of a suitable sheet material are a chop strand matt glassfibre sheet of a mass of 300 to 600 g/m, sheet aluminium, and a melaminetype high pressure laminate.

Again, the first and second lengths of a sheet material may be lengthsof resin impregnated paper as described above.

The thermosetting resin for this purpose may be an unsaturated polyesterresin, a phenol formaldehyde resole resin, or an MDI, preferablythickened with a suitable thickener such as Aerosil, or silica fume. Thepreferred thermosetting resin is an unsaturated polyester resin.

Once the composite product has been made as described above, furtherouter layers may be attached to the composite product. For example, onone or both sides of the composite product there may be attached anouter layer of a finished product of the invention.

Thus for example, there may be made a product comprising the followinglayers one on top of another:

-   an outer layer being a finished product of the invention formed from    a linear low density polyethylene and an unsaturated polyester resin    which has set;-   an intermediate layer being a sheet of paper impregnated with a    resin as described above;-   a core being a finished product of the invention formed from a high    density polyethylene and an unsaturated polyester resin which has    set;-   an intermediate layer of a sheet of paper impregnated with a resin    as described above; and-   an outer layer being a finished product of the invention formed from    a linear low density polyethylene and an unsaturated polyester resin    which has set.

Any one of the layers may also include an amount of polystyrene.Examples of the invention will now be given.

EXAMPLE 1

A feedstock is prepared by mixing the following:

Irradiated high density polyethylene 700 parts by weight Mica 40 mesh200 parts by weight Cenolite hollow glass balloons, 80 to 300 300 partsby weight micron particle size

The feedstock is mixed with:

Isophthalic polyester resin, NCS 993 (NCS Resins) 400 parts by weightCatalyst, Triganox 29B50  6 parts by weight Styrene monomer  60 parts byweight

The mixture is pressed at a temperature of 160° C. to a thickness of 11mm at a density of 825 kg/m³ between first and second lengths of a sheetmaterial, each of the first and second lengths comprising four sheets ofresin impregnated Kraft paper with the weight of 200 g/m² per sheet.

The paper was impreganted with a composition comprising:

Isophthalic polyester resin, NCS 993 20 parts by weight (NCS Resins)Catalyst, Triganox 29B50 0.04 parts by weight DC1107 cross-linkingsiloxane (Dow Corning) 0.20 parts by weight Acetone 79 parts by weightAccelerator, NCS ACI (NCS Resins) 0.06% of 0.10% parts by weight cobaltoctoate in white spirit solution

The solvent is then removed.

A layer of a thermosetting resin is located between the first and secondlengths and the product, viz. NCS 993 isophthalic polyester resin (NCSResins), catalysed with 1.5% Triganox 29B50 and thickened with Aerosilby Degussa. The result is a composite product with a thickness of 15 mm.

The composite product of the invention was tested under load incomparison to a 15 mm birch plywood.

The following test data for a sample with dimensions of 300 mm×300 mmwas obtained.

Maximum applied load - 806 kgf (7907N) Deflection of board of theinvention at maximum load  7.8 mm Deflection of board of the inventionat working load 4.45 mm % strength compared to the 15 mm birch plywoodbased 132% on the ultimate load % strength compared to the 15 mm birchplywood based 106% working load deflection

EXAMPLE 2

An example of a composite suitable for siding or door skins is asfollows:

PERCENTAGE WEIGHT UNIT PVC DB178 (Sasol) 37 900 Fillite SG (Runcorn UK)17 400 Mica 20 mesh 29 700 Orthophthalic Polyester Resin 17 400unsaturated Code 901 (NCS South Africa) 29B50 Triganox (Akzo Chemie) — 4DC 110 (Dow Corning) — 4

The board is pressed to a density of 1100 kg/m³ at a platen temperatureof 185° C. for 8 minutes to a thickness of 8 mm to produce a very strongcomposite of excellent dimensional stability.

EXAMPLE 3

An example of a composition suitable for the production of highperformance boards is as follows:

Component Parts by weight Polystyrene Packaging Waste Grade 150Polyethylene High Density 700 Mica 40 Mesh 600 Hollow Glass Balloons 200901 PA Resin Orthophthalic Unsaturated Polyester NCS 675 29B50 Triganox8 Silane Cross Linker Dow Corning (Adhesion Promoter) 6 Glass Fibre 12mm length 1000 TOTAL 3339

The particle size of the polystyrene particles is 0.5 mm diameter and ofthe polyethylene is 80 mesh.

The above composition was mixed and then pressed at a pressure of 22kg/cm² and at a temperature of 160° C. for eight minutes to a thicknessof 12 mm and a density of 1200 kg/cm³.

A board so produced was tested as a monolithic 12 mm board against a 12mm 9 ply birch plywood board bonded with phenolic resins and surfacedwith a B-stage phenolic resin over the placement sheet on both surfaces.The results are set out below.

12 mm 9 ply Board of birch Shutter Property Unit Invention board TensileStrength MPa 18.1 54.3 Tensile Modulus MPa 534 1601 Flexural StrengthMPa 67.4 43.8 Flexural Modulus MPa 2053 1063 Lap Shear MPa 4.1 15.5Water Absorption (Inc. 24 hrs) % 0.176 30.89 Water Absorption (Inc. 7days) % 1.017 49.02 Area - (Inc. 24 hours) % 0.100 1.477 Area - (Inc. 7days) % 0.139 1.929 Thickness - (Inc. 24 hrs) % 0.353 3.658 Thickness -(Inc. 7 days) % 0.441 6.983 Inc. 24 hrs means increase after 24 hours

The flexural strength and modulus of the board of the invention wererespectively 1½ times and 2 times higher than that of the birch plyshutter board.

Various examples of finished products of the invention will now bedescribed with reference to the accompanying drawings.

Referring to FIG. 1A there is shown a platen 10 of a hydraulic press 12for pressing a profiled shape. A mixture of the feedstock of theinvention with an unsaturated polyester resin in liquid form and acatalyst for the polyester resin, is placed as a layer 14 on the platen10. A profiled mould 16 is then used to press the mixture 14 to form adoor skin moulding illustrated as 18 in FIG. 1B.

As can be seen from FIG. 1B, two door skin mouldings 18 may be joined toeach other. A polyurethane foam may be injected into the space betweenthem to product a polyethylene composite exterior door.

Referring to FIG. 2A there is again shown a platen 20 of a hydraulicpress 22 for pressing a profiled shape. A mixture of the feedstock,polyester resin and catalyst of the invention as described above isplaced as a layer 24 on the platen 22. A profiled mould 26 is used topress the mixture 24 into the mould shapes 28. The mixture 24 firstmelts and then flows into the mould shapes 28 and then sets to form amoulding 30 illustrated in FIG. 2B.

The moulding 30 may be cut into sections 32 for use as window frames.

The unsaturated polyester resin may be replaced by an epoxy resin toproduce similar products:

Referring to FIG. 3 there is shown a wall stud 40 made by the method ofthe invention which may be used in place of a typical 4 inch×2 inch(10.16 cm×5.08 cm) stud of timber. The stud 40 of the invention has avolume advantage over such a conventional timber stud of 25:1 but stillhas a density of 0.95 giving it adequate strength.

Referring to FIG. 4 there is shown a sectioned side view of a length ofdecking 50, made by compression moulding according to the method of theinvention.

Referring to FIG. 5A there is shown a sectioned side view of a sheet 60made by the method of the invention which may be cut to form sidingstrips 62.

Referring to FIG. 5B, the siding strips 62 may be used in a conventionalmanner to provide a siding assembly.

Other finished products of the invention Include corrugated roofsheeting, roof rafters and beams, dismountable bulk handing bins,pallets, stiles and rails for doors, window and door sills, shutterboards or form boards, and the like.

The finished products of the invention have the following advantages.

Polyethylenes, as used in extrusion or other processing, require to becooled before solidification. The use of a polyester in the formulationof the invention allows the polyethylene first to flow, the catalystthen decomposes, and the polyester sets. The finished product so madehas no memory, retains its shape, and may be demoulded at or near theprocess temperature.

By combining a thermoplastic material in dry powder form and athermosetting resin in liquid form, there is no need for pre-compoundingand thus much greater formulation flexibility can be achieved in termsof the quantity and type of extenders that may be included.

As the polyester resin used is reactive, as compared with polyethylenewhich is not reactive, the finished product of the invention may bepainted or glued. This is not possible with an unmodified polyethyleneproduct.

The finished products of the invention have considerable strength as aresult of the materials used therein. In particular the thermosettingresin provides the strength needed for the heterogeneous nature of thethermoplastic resin(s) from a waste stream.

Polyesters and epoxies on polymerisation do not produce a gas, as doother resins such as phenol formaldehyde resole resins and isocyanateresins, which leads to processing advantages, such as the absence ofporosity or blistering.

Because the mixture produced by blending the feedstock with thepolyester or epoxy resin has the properties of both a thermoplastic anda thermoset material, in compression moulding this mixture may beinduced to flow into shapes at a final density gradient of from 0.8 to1.2, i.e 800 to 1200 kg/m³ without materially diminishing thefunctionality of the finished product. Thus, far greater processflexibility can be achieved than would be possible by extrusion.

Polyethylene based extrusions or compression mouldings that containextenders much beyond 20% by weight of the final product exhibit adramatic loss of strength as a function of lack of compatibility oradhesion between the polyethylene and the extender. The use of athermosetting resin in the finished product of the invention overcomesthese problems.

The polyethylene and polystyrene used in manufacture of the finishedproduct of the invention may both be derived from waste product streams,with cost advantages.

1. A method of making a finished product comprising the steps of: a.providing a feedstock which has, (1) 10 to 40 parts by weight of apolymer component comprising, (i) 5 to 100 parts by weight ofpolyethylene in particulate form, and (ii) 0 to 95 parts by weight ofpolystyrene in particulate form, (2) 20 to 70 parts by weight of aparticulate, lightweight volume extender which has a bulk density rangeof from 150 grams per liter to 300 grams per liter, and (3) 0 to 40parts by weight of reinforcing fibers or particles; b. mixing thefeedstock with 10 to 35 parts by weight of an unsaturated polyesterthermosetting resin in liquid form and a catalyst for the thermosettingresin; and c. subjecting the product of step b. to conditions oftemperature between 140° C. and 180° C. and conditions of pressure tocause the polyethylene and the polystyrene, if present, to melt and thethermosetting resin to set to form the finished product.
 2. The methodaccording to claim 1, wherein: (a) the feedstock comprises, (1) 15 to 35parts by weight of the polymer component, (2) 25 to 50 parts by weightof the volume extender, and (3) 0 to 25 parts by weight of thereinforcing fibers or particles; and (b) which is mixed with 15 to 25parts by weight of the thermosetting resin.
 3. The method according toclaim 1, wherein the polyethylene is in powder form and has a particlesize of 1.0 mm diameter or less.
 4. The method according to claim 1,wherein the volume extender is selected from the group consisting of alightweight inorganic volume extender, a lightweight organic volumeextender, milled mineral particles, and mixtures of two or more thereof.5. The method according claim 1, wherein the volume extender is selectedfrom the group consisting of undensified silica fume, exfoliatedvermiculite particles, silica particles and a mixture of two or morethereof.
 6. The method according to claim 1, wherein the volume extenderis in the form of exfoliated vermiculite particles with a particle sizeof less than 300 micron.
 7. The method according to claim 1, wherein thereinforcing fibers or particles are selected from the group consistingof polyester fibers, glass fibers, mica particles, phlogopite particles,lignocellulosic fibers and a mixture of two or more thereof.
 8. Themethod according to claim 1, wherein the reinforcing fibers or particlesare in the form of lignocellulosic fibers.
 9. The method according toclaim 1, wherein in step c. the product of step b. is subjected to apressure of from 10 kg/cm² to 50 kg/cm² inclusive.
 10. The methodaccording to claim 1, further comprising a step between steps b. and c.of placing the product of step b. between first and second lengths ofsheet material so that in step c. the first length and the second lengthare incorporated into the finished product.
 11. The method according toclaim 10, wherein the sheet material is in the form of a resinimpregnated woven fabric.
 12. The method according to claim 10, whereinthe resin impregnated woven fabric comprises a glass fiber sheet.
 13. Amethod of making a finished product comprising the steps of: a.providing a feedstock which has, (1) 15 to 35 parts by weight of apolyethylene polymer component which is in particulate form, (2) 20 to70 parts by weight of exfoliated vermiculite particles which have a bulkdensity range of from 150 grams per liter to 300 grams per liter as avolume extender, and (3) 0 to 25 parts by weight of lignocellulosicfibers as reinforcing fibers, b. mixing the feedstock with 10 to 35parts by weight of an unsaturated polyester thermosetting resin inliquid form and a catalyst for the thermosetting resin; and c.subjecting the product of step b. to conditions of temperature between140° C. and 180° C. and conditions of pressure of from 10 kg/cm² to 50kg/cm² inclusive to cause the polyethylene to melt and the thermosettingresin to set to form the finished product.
 14. The method according toclaim 13, further comprising a step between steps b. and c. of placingthe product of step b. between first and second lengths of sheetmaterial so that in step c. the first length and the second length areincorporated into the finished product.
 15. The method according toclaim 14, wherein the sheet material is in the form of a resinimpregnated woven fabric.
 16. The method according to claim 15, whereinthe resin impregnated woven fabric comprises a glass fiber sheet.
 17. Amethod of making a finished product comprising the steps of: a.providing a feedstock which has, (1) 15 to 35 parts by weight ofpolyethylene in particulate form, (2) 20 to 70 parts by weight ofexfoliated vermiculite particles which have a bulk density range of from150 grams per liter to 300 grams per liter as a volume extender, and (3)0 to 25 parts by weight of lignocellulosic fibers as reinforcing fibers;b. mixing the feedstock with 10 to 35 parts by weight of an unsaturatedpolyester thermosetting resin in liquid form and a catalyst for thethermosetting resin; c. placing the product of step b. between first andsecond lengths of resin impregnated woven fabrics; and d. subjecting theproduct of step c. to conditions of temperature between 140° C. and 180°C. and conditions of pressure of from 10 kg/cm² to 50 kg/cm² inclusiveto cause the polyethylene to melt and the thermosetting resin to set toform the finished product and to cause the first length and the secondlength to be incorporated into the finished product.
 18. A finishedproduct comprising: a polyethylene polymer component; exfoliatedvermiculite volume extender particles which have a bulk density range offrom 150 grams per liter to 300 grams per liter; reinforcing fibers; anunsaturated polyester thermosetting resin; and first and second lengthsof sheet material.
 19. The finished product according to claim 18,wherein the reinforcing fibers comprise lignocellulosic reinforcingfibers.
 20. The finished product according to claim 18, wherein thesheet material comprises glass fiber sheets.